The ultra-clean and high-purity reagents (also called Process Chemicals or Wet Chemicals) are important and basic materials in the production of Very Large-Scale Integration (VLSI). Both ultra-clean and high-purity electronic grade isopropanol and hydrochloric acid are very important and extensively used in producing semiconductors and cleaning corrosion during the assemblage of very large-scale integration etc.
Because of the rapid development of IT technology, the purity requirement of Process Chemicals is higher and higher. Particularly, with the integrated circuit's development and trends towards miniaturization and high speed processing, the requirement of purity is more critical than before. The content of single cation of the electronic grade hydrochloric acid or isopropanol turns into the ppb level from the ppm level, and correspondingly, the standard of the electronic grade hydrochloric acid and isopropanol turns into SEMI-C8 or SEMI-C12 from SEMI-C1 and SEMI-C7 (The SEMI-C is the chemical standard published by Semiconductor Equipment and Material International).
The regular production of liquid Process Chemicals such as hydrochloric acid and isopropanol comprises sub-boiling distillation that uses thermal radiation to hold the liquid phase temperature lower than boiling point and then evaporating and condensing to produce reagents, or rectification. But there is not mature technology for large-scale sub-boiling distillation production, and the concentration of impurities in the electronic grade hydrochloric acid and isopropanol produced with regular rectification is high.
“PURE AND APPLIED CHEMISTRY” (1986, (10): 1412-1418) disclosed a method for the production of ultra-clean and high-purity isopropanol. Adding CaO or Mg powder to reflux with iodine as an activator, and then multiple rectifying to get a product of 99.4% purity and a moisture content of 600 ppm. However, the moisture content of the isopropanol produced through this method is too high.
Bin Zhu etc. reported a method for producing electronic grade isopropanol in “Continuous Production of Electronic Grade Isopropanol from Technical Grade Isopropanol” (NATURAL GAS CHEMICAL INDUSTRY, 2009, 34(2): 67). The continuous production of electronic grade isopropanol is realized through the combination of sub-boiling rectification and batch rectification. The product is in conformity with the CEMI-C8 standard, but the yield is reduced.
Chinese patent No. CN101362675A disclosed a method for the production of ultra-clean and high-purity isopropanol. Industrial grade isopropanol is purified through four-stage rectification. The method of multistage rectification is high risk and requires heavy energy consumption.
Chinese patent No. CN1644487A disclosed a device with which the ultra-clean and high-purity hydrochloric acid can be produced with low temperature evaporation. The hydrochloride passes through two-stage washing columns and bubbling columns and is absorbed by conductivity water in an absorption tower. Then, it is evaporated at a low temperature and finely filtered to produce electronic grade hydrochloric acid. We can see that the equipments used in this invention are complicated.
Chinese patent No. CN1326766C disclosed a method for producing electronic grade hydrochloric acid. The hydrochloride acid produced can be used only as MOS grade or BV-III standard reagent in production of VLSI because of its limited purity.